Audiometer with interchangeable transducer

ABSTRACT

An audiometer including a processor controlled test signal generator is adjustable so as to produce a uniform output signal when coupled with a transducer load. Each transducer set to be used with the test signal generator includes recordable indicia in written or electronic form, upon which correction values for adjusting the electronic signal output of the audiometer module to produce a desired sound output from the each transducer in the transducer set. When the transducer set is connected to the audiometer module, the correction values are either retrieved automatically from the electronic indicia, which may be an EEPROM, or are input to the processor manually by a user through an interface such as a keyboard. These correction values are then used by the processor to dynamically adjust the output of the audiometer to correct for sound output response deviation of each transducer in the transducer set.

RELATED APPLICATION

This application is a continuation of application Ser. No. 11/867498filed Oct. 4, 2007, said application hereby fully incorporated herein byreference, including Appendix A of said application.

FIELD OF THE INVENTION

The instant invention relates to audiometers and more specifically tocalibration of audiometers and associated components.

COMPUTER PROGRAM LISTING APPENDIX

A computer program listing was submitted as Appendix A to the parentapplication Ser. No. 11/867498, the computer program listing consistingof ASCII text files submitted electronically via the USPTO EFS-Websystem. Said Appendix A includes the following files:

TITLE SIZE IN BYTES DATE OF CREATION AppendixA.txt 9,885 Oct. 04, 2007

The entire contents of Appendix A of said parent application is herebyincorporated by reference, including without limitation, theaforementioned files.

BACKGROUND OF THE INVENTION

Audiometers for testing the hearing of human subjects have been inwidespread use for many years. Typically, an audiometer includes a testsignal generator component for generating audio signals, and one or moretransducers for converting the signals to audible sound in the form oftest tones or speech. The test signal generator is often controlled by acomputer or microprocessor so as to enable audio testing of subjects totake place automatically without a highly trained operator inattendance.

Test sounds are typically presented to the test subjects at preciseabsolute sound pressure levels for accuracy, standardization, andcomparison purposes. Due to variability in component values andcharacteristics, however, test signal generators may outputsignificantly different output levels and different transducers mayproduce significantly different absolute sound pressure levels whensupplied with an electrical signal of a uniform value. For thesereasons, the test signal generator and transducers of prior artaudiometers are calibrated together. That is, the test signal generatoris matched to a single transducer set and adjusted to give the desiredabsolute sound pressure levels. An example of such a prior artaudiometer apparatus is disclosed in U.S. Pat. No. 6,468,224 to Foreman,hereby fully incorporated herein by reference.

A drawback of these prior art audiometer systems arises when transducersare lost or damaged. The test signal generator and the specifictransducers that are to be used with the test signal generator in theseprior systems must have been at least once physically connected witheach other and adjusted to ensure the accuracy of the sound pressurelevels output by the transducers. Consequently, if the transducer islost or damaged, a new transducer must be matched and re-calibrated withthe test signal generator. This typically either involves shipping theaudiometer to the original manufacturer or authorized repair location toenable the recalibration and then returning the newly calibratedaudiometer to the service location or requires an on-site visit by askilled repair technician with the proper equipment. Attempts have beenmade to address this problem by including a limited number of sparetransducers, and providing the audiometer with multiple tables ofcorrection values stored therein that can be switched automatically ormanually when a spare transducer is substituted. This, however, is not acompletely satisfactory solution since the transducers and test signalgenerator must still have been once physically connected. Also, oncesupply of spare transducers is depleted, new transducers need to bematched by recalibration on site or at a repair facility. For the user,if a backup audiometer with calibrated transducer is not available, theresult is extended downtime when the audiometer is not available foruse. Moreover, it is often not economically feasible to maintain backupsbecause of the relatively high cost of precision automatic audiometers.

What is still needed in the industry is an audiometer system thatenables any transducer to be used with the test signal generator withouthaving been specifically matched.

SUMMARY OF THE INVENTION

The present invention addresses the needs of the industry for anaudiometer system that enables any transducer to be used with the testsignal generator without having been specifically matched. In anembodiment of the invention, an audiometer module including a processorcontrolled test signal generator is adjustable so as to produce auniform output signal when coupled with a transducer load. Eachtransducer set to be used with the test signal generator includesrecordable indicia in written or electronic form, upon which arerecorded correction value for adjusting the electronic signal output ofthe audiometer module to produce a desired sound output from the eachtransducer in the transducer set. When the transducer set is connectedto the audiometer module, the correction values are either retrievedautomatically from the electronic indicia, which may be an EEPROM, orare input to the processor manually by a user through an interface suchas a keyboard. These correction values are then used by the processor todynamically adjust the output of the audiometer to correct for soundoutput response deviation of each transducer in the transducer set.

According to an embodiment of the invention, an audiometer for testingthe hearing of a test subject includes an audiometer module with a testsignal generator and a processor with associated memory and controllogic operably coupled to the test signal generator. The processorcontrols the test signal generator to generate an electronic test signalhaving a first signal magnitude, and further controls the test signalgenerator to adjust the first signal magnitude to a second signalmagnitude in proportion to a transducer correction value and deliver theelectronic test signal with the second signal magnitude at an output ofthe audiometer module. A transducer is communicatively coupled to theoutput of the audiometer module, wherein the transducer generates asound signal having a desired magnitude when the electronic test signalhaving the second signal magnitude is delivered to the transducer. Thetransducer further comprises a data storage structure with thetransducer correction value is stored therein. The audiometer furtherincludes an interface selectively couplable with the processor fordelivering the transducer correction factor to the processor.

In embodiments of the invention the data storage structure may beelectronic memory such as an EEPROM. In other embodiments, the datastorage structure may be printed indicia attached to the transducer. Theinterface may include a keyboard communicatively coupled directly to theprocessor or to a personal computer communicatively coupled to theprocessor. In embodiments where the data storage structure is electronicmemory, the interface may include a one-wire interface controller.

Embodiments of the invention may also include a method for calibratingan audiometer and a transducer. The audiometer includes a test signalgenerator and a processor, wherein the processor controls the testsignal generator to generate a plurality of electronic test signals eachhaving a first signal magnitude. The processor further controls the testsignal generator to adjust the first signal magnitude of each testsignal to a second signal magnitude in proportion to a correspondingtransducer correction value and to deliver the test signals to an inputof the transducer at the second signal magnitude. The method includesapplying each one of a plurality of input signals to the input of thetransducer, each of the input signals having a signal frequencycorresponding to a signal frequency of one of the test signals, anddetermining a target signal magnitude for each of the plurality of inputsignals that results in a desired magnitude of sound output from thetransducer. For each of the plurality of input signals, a transducercorrection value is determined for the audiometer that results in thecorresponding test signal having a second signal magnitude equal to thetarget signal magnitude determined for the input signal. The transducercorrection values are then stored in a data storage structure associatedwith the transducer. The stored transducer correction values are thendelivered to the audiometer to be used to correct for transducerresponse deviation.

Other embodiments may include a method of calibrating an audiometer andtransducer, the audiometer comprising a test signal generator and aprocessor controlling the test signal generator. The method includesstoring a plurality of transducer correction values in a data storagestructure associated with the transducer, retrieving the transducercorrection values from the transducer using a controller associated withthe audiometer and delivering the retrieved transducer correction valuesto the processor. When a test signal is generated with the test signalgenerator, the processor is used to adjust a magnitude of the testsignal according to at least one of the transducer correction values.The step of storing the plurality of correction values in a data storagestructure associated with the transducer may include writing thecorrection values to an EEPROM or inscribing the correction values on alabel or tag.

An advantage of certain embodiments of the invention is that anytransducer set with which correction values have been associated may beused with an audiometer module without the need for recalibration by atechnician. Furthermore, different types of transducers, such as bonevibrators, sound field speakers, and insert phones may be used andinterchanged without calibration.

The present invention enables a tester to have a fully calibratedsystem, even if the transducers and test signal generator have neverbeen previously connected. The user may receive a set of transducerswith associated correction values, and have a fully calibrated system,even though the components have never been together.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of an embodiment of a computer controlledaudiometer with interchangeable transducer;

FIG. 1 A is a block diagram of a computer controlled audiometer withpersonal computer interface;

FIGS. 2A-2D are each a portion of a block diagram of a computercontrolled audiometer embodying the present invention;

FIGS. 3A-3J are each a portion of a schematic circuit diagram of acentral processing unit module (CPU) of the audiometer of FIG. 2;

FIGS. 4A-4G are each a portion of a schematic circuit diagram of a CPUinput/output section of the audiometer of FIG. 2;

FIGS. 5A-5D are each a portion of a schematic circuit diagram of anoscillator module of the audiometer of FIG. 2;

FIGS. 6A-6D are each a portion of a schematic circuit diagram of anattenuator module of the audiometer of FIG. 2;

FIGS. 7A-7E are each a portion of a schematic circuit diagram of anoutput module of the audiometer of FIG. 2; and

FIG. 8 is a block schematic diagram of a transducer according to anembodiment of the invention.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As depicted in the schematic diagram of FIG. 1, an embodiment of acomputer controlled audiometer with interchangeable transducer system 20generally includes an audiometer module 22 and a transducer set 23including one or more transducers 24. Audiometer module 22 generallyincludes an oscillator 26, variable attenuator 28, final amplifier 29,channel selector switch 29A, a left signal output 30, a right signaloutput 32, a central processing unit (CPU) module 34, and a one-wireinterface controller 36. Transducer set 23 generally includes left andright input jacks 38, 40, transducers 24 coupled thereto with wires 42,44, and a non-volatile memory chip 46. Variable attenuator 28 generallyincludes a plurality of resistor networks 28A, a plurality of magnitudeselector switches 28B, and one or more amplifiers 28C.

In a particular embodiment, a known CCA-100e Computer ControlledAudiometer, available from Benson Medical Instruments of Minneapolis,Minn., may be modified to include the system of the present invention.Oscillator 26, attenuator 28, CPU module 34, left and signal outputs 30,32, as well as ancillary components power supply 50, and CPU I/O section52 are depicted for the example embodiment in block schematic diagramform in FIGS. 2A-2D, and in detailed schematic form in FIGS. 3A-3J and7A-7E.

Transducer set 23 is connected to audiometer module 22 with left inputjack 38 received in left signal output 30 and right input jack 40 inright signal output 32. As depicted in FIG. 1A, and as generally knownin the art, audiometer module 22 can be controlled by a personalcomputer 54, which may include one or more input devices in the form ofa keyboard and/or mouse 56 and a device for presenting information to anoperator such as video display 58.

Typically, audiometer module 22 and transducers 24 are operated toprovide automatic pure-tone hearing threshold testing in accordance withaccepted audiometric procedures, such as for example, the well-knownHughson-Westlake procedure. In one example, CPU module 34 may beprogrammed to position channel selector switch 29A to left signal output30 and to cause oscillator 26 to generate a first test tone of 1 kHz.CPU module 34 then controls magnitude selector switches 28B ofattenuator 28 to present the 1 kHz tone to the left ear of the testsubject through left input jack 38 of transducer 24 at a series ofspecified magnitudes (e.g. 70 dB, 60 dB, 50 dB, 40 dB, 30 db, and 20dB). The test subject responds when the tone is perceived usinghandswitch 60, and the responses may be recorded by audiometer module 22or personal computer 54. Once a threshold is established for the 1 kHztone, the process is repeated for a series of different frequency tones(e.g. 500 Hz, 1 kHz, 2 kHz, 3 kHz, 4 kHz, 6 kHz, and 8 kHz.) toestablish a threshold for each. CPU module 34 then shifts channelselector switch 29A to right signal output 32 and the entire process isrepeated for the right ear of the test subject. It will of course beappreciated that CPU module 34 may be programmed to perform any othersequence or method of testing as may be desired.

In embodiments of the invention, all audiometer modules 22 of a givenmodel may be initially standardized so as to produce a uniform, stableoutput signal, i.e., to generate an electrical output signal having amagnitude within a certain tolerance at any given tone frequency (e.g.500 Hz, 1 kHz, 2 kHz, 3 kHz, 4 kHz, 6 kHz, and 8 kHz) and attenuatorsetting (e.g. 5-100 dB). For example, each CCA-100e Computer ControlledAudiometer, is preferably configured to generate an electrical outputsignal into a stable transducer load to a tolerance of +/−0.3 dB. Bykeeping the output of each audiometer module 22 of a given modelessentially the same, the only variation in the system output resultsfrom variations in conversion of the electrical output signal fromaudiometer module 22 to sound signals in transducers 24.

It will be appreciated that a variety of approaches may be employedwithin the scope of the present invention to enable test signalgenerator output level adjustment. Although a feedback amplifier isdesirable for tightly controlling gain, an impedance network, or even asingle resistor, may be connected in series with the output.

Initial standardization of each audiometer module 22 of a given modelmay be done by testing the output of each audiometer module 22 andstoring initial calibration and correction factors in non-volatile datastorage associated with audiometer module 22. CPU module 34 in eachaudiometer module 22 can then use those initial correction factors tocontrol attenuators 26 to produce an electrical output signal of thedesired uniform magnitude at each of the left signal output 30 and rightsignal output 32. Alternatively, components of audiometer module 22, inparticular those in oscillator 26, attenuators 28 and final amplifier29, may be selected so as to be within specified tolerances (i.e.. ±2%and more preferably ≦±1%). This will ensure that each audiometer module22 of a given model will produce output signals of a uniform magnitudewithin the acceptable range without the need for any initial correctionfactors. Parts and circuits can also be trimmed during manufacturingusing adjustable value components (e.g. potentiometers, variableinductors, etc.) to ensure that each audiometer module 22 producesoutput signals having a uniform magnitude within the acceptable range.

Due to variation in gain, the sound output magnitude from transducers 24of the same make and model for a given signal input magnitude willdeviate, and further, the deviation may vary for signals of differentfrequencies. For example, industry standard TDH-39 transducers typicallyhave an amplitude deviation of up to +/−3 dB for the same input signalmagnitude and frequency. The amount of deviation for each individualtransducer 24 can be determined through acoustic calibration andtesting. To determine the deviation, transducers 24 are connected toaudiometer module 22 and the acoustic output of each transducer 24measured on a sound level meter at each of a set of specifiedfrequencies (e.g. 50 0Hz, 1 kHz, 2 kHz, 3 kHz, 4 kHz, 6 kHz, and 8kHz.). Because the audiometer module 22 output, and therefore themagnitude of the electronic signal input to the transducer, isstandardized as set forth above and is therefore known, transducercorrection values for each frequency to correct for the sound outputdeviation of each transducer 24 can then be determined directly from themeter readings for each transducer 24.

Once the transducer correction values for a transducer 24 have beendetermined, they can be stored electronically on a non-volatile memorychip 46 associated with transducer 24, such as, for example, an EEPROMchip, built into the transducer set 23 or its cabling. In an exampleembodiment depicted in schematic form in FIG. 8, a Dallas SemiconductorDS2431/TO92 EEPROM available from Newark In/One, Chicago, Ill., is builtand wired into the right phone plug associated with transducer set 23.Those of skill in the art will appreciate that any other EEPROM or othernon-volatile memory device may also be used, and any other structure forelectronic interconnection of the non-volatile memory device may also beused while remaining within the scope of the present invention.

One wire interface controller 36, as depicted in schematic form in FIGS.7A-7E, generally includes a protocol bridge device 47 to enableacquisition of the transducer correction values stored on non-volatilememory chip 46 and to transmit them to CPU module 34. In an exemplaryembodiment, protocol bridge device 47 is a Dallas Semiconductor DS2482I²C to 1-Wire® bridge device that interfaces directly to fast (400 kHzmax) I²C master bus 49 coupled to CPU module 34. Firmware logic for theIntel 8051 microcontroller embodiment depicted in FIGS. 1-8 is disclosedin the Computer Program Listing Appendix and is fully incorporated byreference herein.

When transducer 24 is connected to audiometer module 22, the audiometerCPU module 34 reads the transducer correction values from non-volatilememory chip 46 via one-wire interface controller 36, and may store themin non-volatile memory in CPU module 34, such as EEPROM 60. CPU module34 can interrogate the EEPROM before each test or from time to time todetect a change of transducers. When a test signal is subsequentlygenerated by the oscillator 26, the CPU module 34 automatically adjuststhe variable attenuators 28 based on the transducer correction values toadjust the magnitude of the signal output from audiometer module 22 tocorrect for the deviation of the particular transducer 24 being used.Thus, an audiometer module 22 can be used with any transducer 24, andneed not be limited to use with only a certain transducer with which itwas specifically calibrated.

In an alternative embodiment, the transducer correction valuesdetermined when calibrating the transducers 24 can be inscribed on alabel or tag affixed to transducer 24. The date and type of thetransducer 24 may also be included. When a transducer 24 is connected toan audiometer module 22, the user can enter the correction values intopersonal computer 54 via a suitable user interface screen. The personalcomputer 54 then communicates them to the audiometer CPU module 34 viainterface 62, which may be a standard RS-232 serial connection. Logicfor a calibration procedure for an example embodiment using a personalcomputer along with logic enabling a serial connection with audiometermodule 22 is disclosed in the Computer Program Listing Appendix and isfully incorporated by reference herein.

CPU module 34 then automatically adjusts the variable attenuators 28 tocorrect for the deviation from the particular transducer 24 so that thesignal output magnitude of audiometer module 22 results in the desiredabsolute sound signal output magnitude from transducer 24. Inalternative embodiments wherein personal computer 54 is not used as aninterface, a data input device such as a keyboard may be connecteddirectly to CPU module 34 to input the correction values. It will beappreciated that in any of these embodiments, the transducer correctionvalues may be combined with any initial correction values establishedand stored during output standardization of audiometer module 22. Thoseskilled in the art will also recognize that other alternativeembodiments are possible, such as incorporating variation correctingelectronics into the transducer assembly itself.

Transducer response typically varies over a range of a few dB. Forexample, the Telephonics TDH39 may vary plus or minus 3 dB atfrequencies up to 6 kHz and more than that at 8 kHz. Applicable AmericanNational Standards Institute (ANSI) standards require that response becalibrated to within 3dB or better. Because most modern audiometers areadjusted in discrete steps of 1 dB, those of skill in the art areaccustomed to device calibration to within a fraction of a decibel, i.e.plus or minus 0.5 dB. Embodiments of the present invention will enablecalibration within these or even closer tolerances. For instance, with atarget tolerance of equal to or less than 0.5 dB, the present inventioncan enable test signal generator output variation of less than 0.1 dB,and transducer correction values in steps of 0.5 dB. This ensures thatany combinations of test signal generator and transducers would vary byno more than 0.35 dB (0.1 plus half of 0.5 dB). Other combinations oftolerances for each component or the target tolerance itself arepossible within the scope of the present invention. A tolerance of plusor minus 3 dB is desirable for most frequencies, and more desirable isless than 0.5 dB

The embodiments above are intended to be illustrative and not limiting.Additional embodiments are encompassed within the scope of the claims.Although the present invention has been described with reference toparticular embodiments, those skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention. For purposes of interpreting the claims forthe present invention, it is expressly intended that the provisions ofSection 112, sixth paragraph of 35 U.S.C. are not to be invoked unlessthe specific terms “means for” or “step for” are recited in a claim.

1. A method of calibrating an audiometer and earphones for audiometrictesting, the method comprising: normalizing a voltage output level ofthe audiometer; performing acoustical calibration of the earphonesindependent from the audiometer to calculate correction factors for avariety of frequencies; storing the calculated correction factors in anintegrated circuit chip associated with the earphones; connecting theearphones to the audiometer; reading the calculated correction factorsinto the audiometer from the integrated circuit chip associated with theearphones; and creating a composite calibration table based on thecalculated correction factors to set final adjustment factors foroutputting audible test tones from the audiometer.
 2. The method ofclaim 1, wherein acoustical calibration of the earphones is performed atthe same location where the earphones are manufactured.
 3. The method ofclaim 1, further comprising storing information related to the dateand/or revision level of calibration of the earphones in the integratedcircuit chip.
 4. The method of claim 1, further comprising storinginformation related to where and/or by whom the acoustical calibrationof the earphones was performed.
 5. The method of claim 1, furthercomprising storing left and right earphone information in the integratedcircuit chip to ensure proper connection of the earphones to theaudiometer.
 6. The method of claim 1, further comprising storing serialnumber information related to the earphones in the integrated circuitchip.
 7. A method of replacing earphones for use with an audiometer foraudiometric testing, comprising: initially performing the method ofclaim 1 to calibrate the audiometer for use with a first set ofearphones; performing acoustical calibration of a second set ofearphones independent from the audiometer to calculate correctionfactors for the second set of earphones for a variety of frequencies;storing the calculated correction factors for the second set ofearphones in an integrated circuit chip associated with the second setof earphones; discarding the first set of earphones and connecting thesecond set of earphones to the audiometer; reading the calculatedcorrection factors for the second set of earphones into the audiometerfrom the integrated circuit chip associated with the second set ofearphones; and creating a composite calibration table based on thecalculated correction factors for the second set of earphones to setfinal adjustment factors for outputting audible test tones from theaudiometer to the second set of earphones.
 8. A calibrated audiometrictesting system comprising: an audiometer having a normalized voltagelevel output; and a set of independently acoustically calibratedearphones connected to the audiometer, the earphones including anintegrated circuit chip having calibration information stored thereon;wherein the audiometer is operable to read the calibration informationfrom the integrated circuit chip and create a calibration table based onthe calibration information to set final adjustment factors foroutputting audible test tones.
 9. The calibrated audiometric testingsystem of claim 8, wherein the calibration information comprisescorrection factors for each ear calculated for a variety of frequencies.10. The calibrated audiometric testing system of claim 8, wherein theintegrated circuit chip further includes information related to the dateand/or revision level of calibration of the earphones stored thereon.11. The calibrated audiometric testing system of claim 8, wherein theintegrated circuit chip further includes information related to whereand/or by whom acoustical calibration of the earphones was performed.12. The calibrated audiometric testing system of claim 8, wherein theintegrated circuit chip further includes left and right earphoneinformation to ensure proper connection of the earphones to theaudiometer.
 13. The calibrated audiometric testing system of claim 8,wherein the integrated circuit chip further includes serial numberinformation related to the earphones.
 14. A method of calibrating anaudiometer and transducer for audiometric testing, the methodcomprising: standardizing an output signal of the audiometer; performingacoustical calibration of the transducer independent from the audiometerto calculate correction values for a variety of frequencies; storing thecalculated correction values in electronic memory associated with thetransducer; connecting the transducer to the audiometer; reading thecalculated correction values into the audiometer from the electronicmemory associated with the transducer; and creating a compositecalibration table based on the calculated correction values to set finaladjustment factors for outputting audible test tones from theaudiometer.
 15. The method of claim 14, wherein acoustical calibrationof the transducer is performed at the same location where the transduceris manufactured.
 16. The method of claim 14, further comprising storinginformation related to the date and/or revision level of calibration ofthe transducer in the electronic memory.
 17. The method of claim 14,further comprising storing information related to where and/or by whomthe acoustical calibration of the transducer was performed.
 18. Themethod of claim 14, further comprising storing left and right transducerinformation in the electronic memory to ensure proper connection of thetransducer to the audiometer.
 19. The method of claim 14, furthercomprising storing serial number information related to the transducerin the electronic memory.
 20. The method of claim 14, furthercomprising: performing acoustical calibration of a second transducerindependent from the audiometer to calculate correction values for thesecond transducer for a variety of frequencies; storing the calculatedcorrection values for the second transducer in electronic memoryassociated with the second transducer; discarding the first transducerand connecting the second transducer to the audiometer; reading thecalculated correction values for the second transducer into theaudiometer from the electronic memory associated with the secondtransducer; and creating a composite calibration table based on thecalculated correction values for the second transducer to set finaladjustment factors for outputting audible test tones from the audiometerto the second transducer.
 21. A calibrated audiometric testing systemcomprising: an audiometer having a standardized output level; and anindependently acoustically calibrated transducer connected to theaudiometer, the transducer including electronic memory havingcalibration information stored therein; wherein the audiometer isoperable to read the calibration information from the electronic memoryand create a calibration table based on the calibration information toset final adjustment factors for outputting audible test tones.
 22. Thecalibrated audiometric testing system of claim 21, wherein thecalibration information comprises correction factors for each earcalculated for a variety of frequencies.
 23. The calibrated audiometrictesting system of claim 21, wherein the electronic memory furtherincludes information related to the date and/or revision level ofcalibration of the transducer stored thereon.
 24. The calibratedaudiometric testing system of claim 21, wherein the electronic memoryfurther includes information related to where and/or by whom acousticalcalibration of the transducer was performed.
 25. The calibratedaudiometric testing system of claim 21, wherein the electronic memoryfurther includes left and right earphone information to ensure properconnection of the transducer to the audiometer.
 26. The calibratedaudiometric testing system of claim 21, wherein the electronic memoryfurther includes serial number information related to the transducer.